1. Field of the Invention
This invention relates to a thermal processing unit for a single substrate.
2. Disclosure of the Prior Art
In some processes for manufacturing semiconductor device, various types of thermal processing unit are used in order to conduct a process such as an oxidation, a diffusion, a CVD or an annealing onto a substrate such as a semiconductor wafer. As one of the thermal processing units, a thermal processing unit for a single substrate is known, which can conduct a thermal process to semiconductor wafers one by one. The thermal processing unit for a single substrate can conduct a thermal process involving a rapid rise and fall of temperature thereof, which is suitable for large-sized semiconductor wafers and/or minute semiconductor devices.
In a conventional hot-wall type of the thermal processing unit for a single substrate, a single semiconductor wafer as a single substrate is conveyed into a processing chamber while supported by a supporting body attached on an upper end of an elevating shaft. Then, the semiconductor wafer is heated in a predetermined atmosphere of a process gas by a heater arranged outside the processing chamber in order to undergo a thermal process. In the case, the supporting body is adapted to support a lower surface of the semiconductor wafer with a plurality of points, for example with three points. A preprocessed semiconductor wafer is conveyed onto the supporting body by a conveying arm arranged at a platform side. After the semiconductor wafer has undergone the thermal process, the semiconductor wafer is conveyed out from the supported body.
However, in the conventional thermal processing unit for a single substrate, the semiconductor wafer is supported with the three points while undergoing the thermal process. Thus, stress tends to concentrate on each of the three points, which may cause a crystal defect. In addition, heat is given to the semiconductor wafer mainly from a peripheral area (edge area) thereof. Thus, in heating the semiconductor wafer, a temperature of a central area thereof may be delayed rising with respect to that of t he peripheral area thereof. As a result, ununiformity (difference) in temperature distribution within a surface of the wafer may be caused in the heating process.
This invention is intended to solve the above problems effectively. An object of this invention is to provide a thermal processing unit for a single substrate that can restrain concentration of stress onto the substrate and conduct a thermal process uniformly within a surface of the substrate.
This invention is characterized by a feature wherein a thermal processing unit for a single substrate comprises: a processing chamber vessel whose inside can be made a predetermined atmosphere of a process gas; an elevating shaft which can be moved up and down in the processing chamber vessel; a supporting body arranged on an upper end of the elevating shaft, which can support a substrate; and a heater for heating the substrate supported by the supporting body; wherein the supporting body has a circular supporting part which can support a substantially full surface of a peripheral area of the substrate, and a pushing-up member which can push up the substrate from the supporting part for conveying the substrate.
According to the feature, concentration of stress onto the substrate can be restrained, and a thermal process can be conducted uniformly within a surface of the substrate because heating from a peripheral area of the substrate may be restrained. In addition, the substrate can be easily conveyed although the substantially full surface of the peripheral area of the substrate is supported.
Preferably, a ring part is provided on the supporting part for surrounding the peripheral area of the substrate.
Preferably, the pushing-up part has a plurality of point-supporters.
For example, the elevating shaft has an outside pipe and an inside rod, the supporting part of the supporting body is provided on an upper end of the outside pipe, and the pushing-up member of the supporting body is provided on an upper end of the inside rod.
In the case, preferably, a temperature measuring gauge is connected to the inside rod of the elevating shaft. Alternatively, a temperature measuring gauge is connected to the outside pipe of the elevating shaft.
Preferably, the outside pipe of the elevating shaft and the circular supporting part of the supporting body are hermetically connected via a tubular or funnel-shaped connector.
Preferably, a built-in heater is incorporated in the supporting body for maintaining a temperature of the supporting body at a substantially constant temperature.
In the case, preferably, the supporting body has a bottom part facing a central area of the substrate, and the built-in heater is provided in the bottom part. More preferably, the bottom part is formed convexly toward the central area of the substrate, and the built-in heater is also arranged convexly toward the central area of the substrate.
In addition, a showerhead may be provided at an upper portion of the processing chamber vessel for introducing a process gas into the processing chamber vessel. In the case, preferably, the showerhead is formed convexly toward the central area of the substrate.
In addition, for example, the heater is arranged outside the processing chamber vessel in such a manner that the heater oppositely faces a surface of the substrate. In the case, the heater may consist of a resistance heater.
Alternatively, the heater is arranged outside the processing chamber vessel and spherically around a center of the substrate. In the case, the heater may consist of a plurality of heating lamps. Preferably, a heat-radiating direction of each of the plurality of heating lamps is adjustable.
In addition, preferably, an assistant heater is provided outside the processing chamber vessel for heating an area other than a thermal processing area for the substrate.